Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$152.86	6.178%	$162.3037	$162.30	$162.30	$162.30
Purchase #2	$235.90	10.533%	$260.7473	$260.75	$260.75	$260.70
Purchase #3	$114.91	11.243%	$127.8293	$127.83	$127.85	$127.80
Purchase #4	$68.79	7.431%	$73.9018	$73.90	$73.90	$73.90
Purchase #5	$71.58	13.699%	$81.3857	$81.39	$81.40	$81.40
Purchase #6	$179.45	4.704%	$187.8913	$187.89	$187.90	$187.90
Purchase #7	$250.27	6.636%	$266.8779	$266.88	$266.90	$266.90
7 purchase totals =	$1,073.76		$1,160.9370	$1,160.94	$1,161.00	$1,160.90